GB2242333A

GB2242333A - Test card generator

Info

Publication number: GB2242333A
Application number: GB9100068A
Authority: GB
Inventors: Winfried Deckelmann; Hans-Peter Richter; Stefan Ott
Original assignee: BTS Broadcast Television Systems GmbH
Current assignee: Philips GmbH
Priority date: 1990-01-09
Filing date: 1991-01-03
Publication date: 1991-09-25
Anticipated expiration: 2011-01-03
Also published as: JPH04280192A; US5038210A; GB2242333B; DE4000359A1; GB9100068D0

Description

:2 -711 4:2:3;3 ---3 A 11 v TEST CARD SIGNAL GENERATOR This Invention

relates to a test card signal generator based on the zone Plate principle.

Patent Specification No. GB 2,206,013 A discloses a generator for generating circular zone.plate signals for testing digital television circuits. However, this generator cannot generate test signals other than zone plate signals.

It is an object of the present invention to provide a test card signal generator, based on the zone plate principle, for generating different test signal shapes.

According to the present invention there is provided a test card signal generator based on the zone plate principle for producing different test signal shapes, comprising pixel and line counters for producing an orthogonal scanning raster, a respective read-only memory connected to each counter for producing H and V-frequency phase values, an adder stage for combining these phase values, and a third read-only memory for converting the phase values into amplitude values, wherein a fourth read-only memory for weighting the scanning raster produced with a square root function is selectively connectable between the adder stage and the third read-only memory The invention has the advantage that for very little additional circuitry it is possible to produce a large number of complex test patterns-.

The invention further provides a test card signal generator based on the zone plate principle for producing different test signal shapes, comprisingpixel and line counters for producing an orthogonal scanning raster, a respective read-only memory connected to each counter for producing H and Vfrequency phase values, an adder stage for combining these phase values, and a third read- only memory for converting the phase values into amplitude values, further including a microprocessor for loading the read-only memories with different functions so that a variable scanning raster can be provided at the output of the adder stage.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawing, which is a block circuit diagram of a test card signal generator.

Referring to the drawing, a pixel counter 1 clocked with a scanning (pixel) clock CLK is reset with 1 1 ti 1 k each H-frequency pulse signal. A line counter 2 clocked with the H- frequency pulse signals is reset by each 2V pulse signal. The 12 bit output signals of the counter 1 and the counter 2 can produce an orthogonal scanning raster. A first read-only memory 3 is connected to the output of the counter 1 and a second read-only memory 4 is connected to the output of the counter 2, and these are programmed to generate the phase values of horizontal and vertical sweep signals respectively. As a result of the orthogonality of the scanning raster, these phase values can be linearly superimposed in a following adder stage 5. A signal with a qv.adratically rising phase can then be taken at the output of the adder stage 5 if the read-only memories 3 and 4 each contain a parabolic function.

The output of the adder stage 5 is connected to a switch 7, on one hand directly and on the other hand across a further read-only memory 6 which is programmed with a square root function. In the lower position of the switch 7, as shown in the drawing, the output signal -: supplied by the adder stage 5 is fed across the read-only memory 6, so that a phaselinear signal is then produced by the root function. For example, a round colour bar can be generated by the read-only memory i 6. For this purpose a square function is loaded into the read-only memories 3 and 4, so that the equation of a circle is fulfilled-- In obtain equidistant spacing s of the individual colour bars, the scanning raster must be weighted with a root function after the adder stage-5, Thus, each monodimensional test card can be represented in circular form When the switch 7 is placed in the upper position, the conventional zone plate signal is passed on.

In a following further adder stage 8 it is possible to feed in a time component, for example a time sweep signal or a constant movement frequency signal. The output of the further adder stage 8 is connected to a following read-only memory 9, which converts the phase values supplied thereto as address signals into amplitude values. The output of the readonly memory 9 is connected to an output 13, on one hand directly and on the other hand across a read- only memory 11 for producing marks which can be faded in via a further switch 12.

In order to be able to produce and represent further complex test signals, a microprocessor 14 (or EPROM) controllable via input lines E is provided, permitting different data to be loaded into the ROMs 1 ii 11, d :. L I' 3, 4 and 9. Thus, for example, the parabolic function stored in the memories 3 and 4 can be replaced by the equation of a straight line or a constant, also in a different arrangement. The curve shape stored in the memory 9 can also be changed by control from the microprocessor 14, to bring about a modification to the test signal. The time component supplied to the adder stage 8 can also be controlled across an accumulator 10 means 15 by the microprocessor 14.

Claims

1. A test card signal generator based on-the zone plate principle for producing different test signal-shapes, comprising pixel and line counters for producing an orthogonal scanning raster,-arespective read- only memory connected to each counter for producing H and V-frequency phase values, an adder stage for combining these phase values, and a third read-only memory for converting the phase values into amplitude values, wherein a fourth read-only memory for weighting the scanning raster produced with a square root function is selectively connectable between the adder stage and the third read-only memory.

2. A test card signal generator as..:claimed in claim 1, further including a microprocessor for loading the third read-only memory with different curve shapes.

3. A test card signal generator as claimed.in claim 2, wherein a further adder stage is provided after the fourth read-only memory for adding a time component controlled by the microprocessor.

4. A test card signal generator as claimed in claim 1, wherein a fifth read-only memory for fading f 4 0. W k_ in marks is selectively connectable in the test signal path following the adder stage.

1

5. A test card signal generator based on the zone plate principle for producing different test signal shapes, comprising pixel and line counters for producing an orthogonal scanning raster, a respective read-only memory connected to dach counter for producing H and V-frequency phase values.

an adder stage for combining these phasevalues, and a third read-only memory for converting the phase values into amplitude values, further including a microprocessor for loading the read only memories with different functions so that a variable scanning raster can be provided at the output of the adder stage.

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6. A test card signal generator substantially as described with reference to the accompanying 20 drawing.

Published 3 99 1 at The Patent Office. Concept House. Cardiff Road. NeuTort. GATni NP9) RH Further copies may be obtained from Sales branch. Unit 6. NmeMile Point. CAmfelinfach. Cross Keys. Newport. NP) 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.